General Session: Diagnostic Imaging

Presented by: G. McBride

Author(s):

G. McBride(1)

(1) Orlando Orthopedic Center, Spine Center, Orlando, FL, United States

Abstract

Objective: This study was designed to develop a new grading system to evaluate lumbar foraminal stenosis based on the anatomic shape of the lumbar foramen. Current grading systems i.e. mild, moderate, and severe frequently utilized by radiologists do not seem to reflect accurately anatomic altertions in the foramin that could explain radicular symptoms.

Materials and Methods: Five grades were developed to evaluate lumbar foraminal stenosis based on simple anatomic shape of the pedicle based on sagittal MRI images. Alterations of the anatomic shape are believed to correlate more closely with radicular symptoms. Grade 1 refers to the normal "oval" shape of the foramin. Grade 2 refers to slight narrowing of the lower half of the "oval" but probably causes only mild impingement. Grade 3 refers to further narrowing of the lower half of the "oval" where the foramin overall shape has the appearance of a "tennis racket" and likely causes moderate impingement on the exiting nerve root. Grade 4 refers to preservation of the top or "head portion" of the "tennis racket" but complete loss of the "handle" portion of the "tennis racket" so that it is either non-existent or a narrowed to very thin line and likely causes severe impingement. Grade 5 refers to reduced size of the top of the "tennis racket " or "head" or it's complete obliteration also reflecting severe impingement. Three experienced spine surgeons reviewed 120 foramins from L3-4 to L5-S1 in 20 MRI studies of symptomatic patients and the foramins were ranked from Class 1 to 5 and interobserver agreement was analyzed.

Results: Interobserver agreement was 100% for Grade 1, 95% for Grade 2, 92% for Grade 3 and 4, and 90% for Grade 5. Correlation to the symptomatic level and laterality of the radicular pain was 85% and 82%.

Conclusion: The new classification system for forminal stenosis based on anatomic shape appears to demonstate a high correlation between spinal surgeon observers and may help explain clinically relevant symptoms.